1. Field of the Invention
The present invention relates to a dielectric electronic component such as a dielectric filter or a dielectric duplexer including a plurality of resonators arranged in parallel and adapted to use in a mobile communication device such as a cellular telephone.
2. Description of the Related Art
Conventional dielectric electronic components include a dielectric filter having a configuration as described below.
Referring to FIG. 1 of the accompanying drawings, the dielectric filter F comprises a substantially rectangularly parallelepipedic dielectric ceramic block B, resonators r1 and r2 arranged in parallel in a given direction and excitation holes t1 and t2 arranged at the opposite outer lateral sides of the resonators r1 and r2. Each of the resonators r1 and r2 includes a through hole provided in the dielectric ceramic block B, each through hole having an inner peripheral surface coated with an internal conductor. Each of the excitation holes t1 and t2 has an inner peripheral surface coated with an internal conductor.
The top surface e of the dielectric ceramic block B defines the open-circuiting ends a1 and a2 of the resonators r1 and r2 and the short-circuiting ends b1 and b2 of the excitation holes t1 and t2. The bottom surface f of the dielectric ceramic block B defines the short-circuiting ends of the resonators r1 and r2 and the open-circuiting ends of the excitation holes t1 and t2. Then, the outer surfaces of the dielectric block B are coated with an external conductor g by means of a known technique such as screen printing except regions surrounding the open-circuiting ends a1 and a2 of the resonators r1 and r2 and those surrounding the open-circuiting ends of the excitation holes t1 and t2. Therefore, the resonators r1 and r2 and the excitation holes t1 and t2 are connected to the external conductor g at the short-circuiting ends thereof and isolated from the external conductor g by respective insulating sections at the open-circuiting ends thereof.
The length of the resonators r1 and r2, or the resonance length, is made substantially equal to xc2xc of the resonance wavelength xcex. The resonator r1 and the excitation hole t1 are electromagnetically coupled. So are the resonator r2 and the excitation hole t2. An input/output pad P1 is formed at a position close to the open-circuiting end of the excitation hole t1 on a lateral surface of the dielectric ceramic block B as extension of the internal conductor of the excitation hole t1. Similarly, another input/output pad P2 is formed at a position close to the open-circuiting end of the excitation hole t2 on the same lateral surface of the dielectric ceramic block B as extension of the internal conductor of the excitation hole t2. The input/output pads P1 and P2 are formed isolated from the external conductor g.
Meanwhile, dielectric filters having the above described configuration are always required to show a desired reflection characteristic. It is necessary to adjust the extent of input/output coupling in order to acquire a desired reflection characteristic. Known means for adjusting the extent of input/output coupling include those that are adapted to do so by regulating the diameter and the positions of the excitation holes.
In the dielectric filter F having the above described configuration, the internal conductors of the excitation holes t1 and t2 are formed normally by drawing an electrically conductive material from an end of each of the excitation holes by vacuum and applying the conductive material to the inner peripheral surfaces of the excitation holes. On the other hand, the external conductor g is laid on the short-circuiting end facets of the top surface e of the dielectric ceramic block B where the short-circuiting ends b1 and b2 of the excitation holes t1 and t2 are formed. This external conductor g is normally produced by a known printing technique such as screen printing.
However, to meet the demand for down-sized devices that has remarkably increased in recent years, dielectric filters are required to show reduced dimensions. Under these circumstances, it is often difficult to modify the diameter of the excitation holes to a desired value and hence it is no longer possible to adjust the extent of input/output coupling over a wide range in a dielectric filter. Then, such a dielectric filter can find only a limited scope of application. Dielectric duplexers face similar problems.
Additionally, known dielectric filters having the above described configuration are accompanied by a problem of a large number of manufacturing steps and high manufacturing cost because they are manufactured by forming internal conductors on the excitation holes and external conductors on the short-circuiting end facets of the excitation holes independently in separate respective printing steps. Furthermore, there are occasions where each of the internal conductors of the excitation holes desirably has a given thickness in a given region thereof. There are also occasions where they desirably have a given surface area. Again, dielectric duplexers face similar problems.
In view of the above identified problems, it is therefore the object of the present invention to provide a dielectric electronic component such as a dielectric filter or a dielectric duplexer that can dissolve those problems.
In an aspect of the invention, the above object is achieved by providing a dielectric electronic component for a communication device comprising:
a plurality of resonators provided in a dielectric ceramic block, each of which includes a through hole bored through the dielectric ceramic block and having an inner peripheral surface coated with an internal conductor;
a plurality of excitation holes formed in the dielectric ceramic block and electromagnetically coupled with the resonators, each of which has an inner peripheral surface coated with an internal conductor, said resonators and said excitation holes being arranged in parallel;
the dielectric ceramic block having a top surface on which open-circuiting ends of the resonators and short-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having a bottom surface on which short-circuiting ends of the resonators and the open-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having an outer peripheral surface coated with an external conductor except regions surrounding the open-circuiting ends of the resonators and those of the excitation holes; and
the short-circuiting ends of the excitation holes being provided with respective coupling-adjusting countersinks showing an increased diameter.
With the above defined arrangement, the input/output coupling of the dielectric electronic component can be weakened without raising the outer dimensions of the dielectric electronic component.
In another aspect of the present invention, there is provided a dielectric electronic component for a communication device comprising:
a plurality of resonators provided in a dielectric ceramic block, each of which includes a through hole bored through the dielectric ceramic block and having an inner peripheral surface coated with an internal conductor;
a plurality of excitation holes formed in the dielectric ceramic block and electromagnetically coupled with the resonators, each of which has an inner peripheral surface coated with an internal conductor, said resonators and said excitation holes being arranged in parallel with each other;
the dielectric ceramic block having a top surface on which open-circuiting ends of the resonators and short-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having a bottom surface on which short-circuiting ends of the resonators and the open-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having an outer peripheral surface coated with an external conductor except regions surrounding the open-circuiting ends of the resonators and those of the excitation holes; and
the open-circuiting ends of the excitation holes being provided with respective coupling-adjusting countersinks each having an increased diameter.
With the above defined arrangement, the input/output coupling of the dielectric electronic component can be strengthened without raising the outer dimensions of the dielectric electronic component.
According to another aspect of the invention, there is also provided a method of adjusting a coupling of a dielectric electronic component such as a dielectric filter or a dielectric duplexer by modifying the depth of the countersinks provided for the purpose of adjusting the extent of coupling.
With such a method, it is possible to adjust the extent of input/output coupling of a dielectric electronic component without raising the outer dimensions of the dielectric electronic component.
In another aspect of the present invention, there is provided a dielectric electronic component such as a dielectric filter or a dielectric duplexer comprising:
a plurality of resonators provided in a dielectric ceramic block, each of which includes a through hole bored through the dielectric ceramic block and having an inner peripheral surface coated with an internal conductor;
a plurality of excitation holes formed in the dielectric ceramic block and electromagnetically coupled with the resonators, each of which has an inner peripheral surface coated with an internal conductor, said resonators and said excitation holes being arranged in parallel;
the dielectric ceramic block having a top surface on which open-circuiting ends of the resonators and short-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having a bottom surface on which short-circuiting ends of the resonators and the open-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having an outer peripheral surface coated with an external conductor except regions surrounding the open-circuiting ends of the resonators and those of the excitation holes; and
the top surface of the dielectric ceramic block including an open-circuiting end facet defining the open-circuiting ends of the resonators and coupling-adjusting setback facets, said setback facets being recessed by a predetermined distance from the top surface and defining short-circuiting ends of the excitation holes.
With the above defined arrangement, again the input/output coupling of the dielectric electronic component can be weakened without raising the outer dimensions of the dielectric electronic component.
In another aspect of the present invention, there is provided a dielectric electronic component for a communication device comprising:
a plurality of resonators provided in a dielectric ceramic block, each of which includes a through hole bored through the dielectric ceramic block and having an inner peripheral surface coated with an internal conductor;
a plurality of excitation holes formed in the dielectric ceramic block and electromagnetically coupled with the resonators, each of which has an inner peripheral surface coated with an internal conductor, said resonators and said excitation holes being arranged in parallel with each other;
the dielectric ceramic block having a top surface on which open-circuiting ends of the resonators and short-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having a bottom surface on which short-circuiting ends of the resonators and the open-circuiting ends of the excitation holes are defined;
the dielectric ceramic block having an outer peripheral surface coated with an external conductor except regions surrounding the open-circuiting ends of the resonators and those of the excitation holes; and
the bottom surface of the dielectric ceramic block including a short-circuiting end facet defining the short-circuiting ends of the resonators and coupling-adjusting setback facets, said setback facets being recessed by a predetermined distance from the bottom surface and defining open-circuiting ends of the excitation holes.
With the above defined arrangement, again the input/output coupling of the dielectric electronic component can be strengthened without raising the outer dimensions of the dielectric electronic component.
According to a further aspect of the present invention, there is also provided a method of adjusting coupling of a dielectric electronic component such as a dielectric filter or a dielectric duplexer by modifying the depth of the setback facets provided for the purpose of adjusting the extent of coupling. With such a method, it is possible to adjust the extent of input/output coupling of a dielectric electronic component without raising the outer dimensions of the dielectric electronic component.
In another aspect of the present invention, there is provided a dielectric electronic component for a communication device comprising:
a plurality of resonators provided in a dielectric ceramic block, each of which includes a through hole bored through the dielectric ceramic block and having an inner peripheral surface coated with an internal conductor;
a plurality of excitation holes formed in the dielectric ceramic block and electromagnetically coupled with the resonators, each of which has an inner peripheral surface coated with an internal conductor, said resonators and said excitation holes being arranged in parallel;
either a top surface or a bottom surface of the dielectric ceramic block being provided with open-circuiting ends of the resonators and short-circuiting ends of the excitation holes;
either the bottom surface or the top surface, whichever appropriate, of the dielectric ceramic block being provided with short-circuiting ends of the resonators and the open-circuiting ends of the excitation holes;
an outer peripheral surface of the dielectric ceramic block being coated with an external conductor except regions surrounding the open-circuiting ends of the resonators and those of the excitation holes; and
either the top surface or the bottom surface, whichever appropriate, of the dielectric ceramic block including an open-circuiting end facet that defines the open-circuiting ends of the resonators and setback facets to be coated with a conductor, said setback facets being recessed by a predetermined distance from the top surface or the bottom surface, whichever appropriate, and defining short-circuiting ends of the excitation holes.
With the above defined arrangement, it is possible to integrate the step of forming internal conductors respectively on the inner peripheral surfaces of the excitation holes and the step of forming external conductors respectively on the setback facets to be coated with a conductor that define the short-circuiting ends of the excitation holes. For example, an electrically conductive material such as silver paste is drawn by vacuum from the open-circuiting end toward the short-circuiting end of each of the excitation holes to form an internal conductor on the inner peripheral surface thereof. The electrically conductive material that gets to the end of the excitation hole, which becomes a short-circuiting end, will flow on the surface of the setback facet. The surface of the setback facet is perpendicular relative to the inner peripheral surface of the excitation hole. In this way, an external conductor is formed. Therefore, the internal conductors of the excitation holes and the external conductors surrounding the short-circuiting ends of the excitation holes can be formed in the step of drawing an electrically conductive material by vacuum. Thus, the printing step is simplified in the case of the above arrangement because the surface areas where the external conductors are formed are clearly defined.
In a dielectric electronic component as defined above, it may additionally be so arranged that the open-circuiting ends of the excitation holes are provided with respective countersinks to be coated with a conductor that show an increased diameter in either the bottom surface or the top surface, whichever appropriate, of the dielectric ceramic block. With this arrangement, the entire surface area of the internal conductors formed on the inner peripheral surfaces of the excitation holes is enlarged if compared with an arrangement without countersinks to be coated with a conductor. In other words, the effective length of the excitation holes is increased. Internal conductors can be formed at desired locations to a desired thickness and the surface area of the internal conductors can be regulated by appropriately selecting a depth, a diameter and a profile for the countersinks to be coated with a conductor. In other words, it is possible to regulate the effective length of the excitation holes.
In another aspect of the present invention, there is provided a dielectric electronic component for a communication device comprising:
a plurality of resonators provided in a dielectric ceramic block, each of which includes a through hole bored through the dielectric ceramic block and having an inner peripheral surface coated with an internal conductor;
a plurality of excitation holes formed in the dielectric ceramic block and electromagnetically coupled with the resonators, each of which has an inner peripheral surface coated with an internal conductor, said resonators and said excitation holes being arranged in parallel;
either a top surface or a bottom surface of the dielectric ceramic block being provided with open-circuiting ends of the resonators and short-circuiting ends of the excitation holes;
either the bottom surface or the top surface, whichever appropriate, of the dielectric ceramic block being provided with short-circuiting ends of the resonators and the open-circuiting ends of the excitation holes;
an outer peripheral surface of the dielectric ceramic block being coated with an external conductor except regions surrounding the open-circuiting ends of the resonators and those of the excitation holes; and
one of the opposite ends of each of the excitation holes being provided with a countersink to be coated with a conductor showing an increased diameter.
With the above arrangement, the surface area of the internal conductors of the excitation holes can be enlarged because the inner peripheral surfaces of the countersinks to be coated with a conductor are also provided with an internal conductor. Thus, according to the invention, internal conductors can be formed in desired conditions by appropriately selecting a depth, a diameter and a profile for the countersinks to be coated with a conductor. In other words, it is possible to regulate the effective length of the excitation holes.
In a dielectric electronic component as defined above, it may additionally be so arranged that both the short-circuiting end and the open-circuiting end of the opposite ends of each of the excitation holes are provided with a countersink to be coated with a conductor that shows an increased diameter. With this arrangement, it is possible to form an internal conductor at both the short-circuiting end and the open-circuiting end of each of the excitation holes in desired conditions. Additionally, since countersinks to be coated with a conductor are formed in the inside of the dielectric ceramic block, the outer profile of the dielectric ceramic block is prevented from becoming uneven. Therefore, a known printing technique such as screen printing can advantageously be used for coating the outer surfaces of the dielectric ceramic block with an external conductor.
As pointed out above, a dielectric electronic component according to the invention is typically a dielectric filter or a dielectric duplexer.